1/TINH
\(\frac{3}{2}-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}+\frac{19}{90}\)
\(\frac{2^3}{1.3}.\frac{3^2}{2.4}.\frac{4^2^{^{^{ }}}}{3.5}......\frac{99^2}{98.100}\)
2/CMR
\(\frac{1}{4}+\frac{1}{16}+\frac{1}{36}+\frac{1}{64}+\frac{1}{100}+\frac{1}{144}+\frac{1}{196}+...+\frac{1}{10000}< \frac{1}{2}\)